Moisture proof connector for spark plugs



g- 1, 1967 c. D. BESORE ETAL. 3,334,326

MOISTURE PROOF CONNECTOR FOR SPARK PLUGS Filed July 6,. 1965 FIG. 3.

, I I I INVENTORS CHARLES D. BESORE,

REX 0 P/AKLE 5) 7195/2 ATTORNEYS HARE/5, K/EcH, RUSSELL & KERN UnitedStates Patent 3,334,326 MOISTURE PROOF CONNECTOR FoR SPARK PLUGS Thepresent invention relates generally to the internal combustion engineart and more particularly to a novel moisture proof connector for sparkplugs which is especially useful with aircraft type spark plugs whichare susceptible to fouling due to the accumulation of moisture and dirtin the spark plug well.

The subject connector is for use with a spark plug which includes acylindrical barrel with an upper end with external threads adjacentthereto, a tubular insulator with an upper end positioned within thebarrel, and a contact terminal within the insulator adjacent the lowerend thereof, and briefly stated one embodiment of the present inventionincludes an insulated electrical cable which includes contact means atone end thereof for engagement with the contact terminal of the plug,and a tubular grommet of resiliant material which is adaptedto fitwithin the barrel of the plug and which includes internal flanges forsealing engagement with the cable, an external annular projection orcollar having an outer peripheral wall surface which is adapted toengage the inner wall surface of the plug barrel and which also includesa lower shoulder adapted to seat upon the upper end of the insulator ofthe plug. Positioned on the tubular grommet above the annular projectionis a rigid tubular ferrulewhich has an O-ring mounted thereon, theO-ring being adapted to seat upon the upper end of the plug barrel whenthe aforementioned lower shoulder of the grommet projection is inengagement with the upper end of the insulator. A nut is rotatablymounted on the ferrule for engagement with the threads carried by theupper end of the plug barrel, whereby when said nut is screwed onto theplug barrel, the lower shoulder of the grommet projection is forced intosealing engagement with the upper end of the insulator, the peripheralwall of the grommet projection is forced outwardly into sealingengagement with the inner wall of the plug barrel, and the O-ring isforced into sealing engagement with the upper endof the plug barrel.

As is well known in the aircraft art, there is a tendency for moistureand dirt to enter the well of spark plugs used with aircraft engineswith the undesirable and sometimes disastrous result that the plugmisfires, with resulting poor engine performance or engine failure.

It is an object of the present invention, therefore, to provide a novelconnector for spark plugs which impedes the entrance of moisture anddirt into the spark plug well. More particularly, it is an object toprovide such a connector which includes sealing means between the cableand the connector, and three circumferential sealing areas between theconnector and the spark plug proper to seal off the interior of thespark plug from the surrounding atmosphere.

Another object is to provide such a novel connector which is relativelysimple in construction, which has relatively few parts, and whichi-srelatively inexpensive to manufacture.

An additional object is to provide a novel moisture proof connector forspark plugs which is easy to install and service by even the mostinexperienced personnel.

Further objects and advantages of the present invention will be apparentfrom the following detailed description, reference being had to theaccompanying drawing where- "ice in a prefered embodiment of the presentinvention is shown.

In the drawing:

FIG. 1 is a side elevational view of a novel moisture proof connectorembodying the teachings of the present invention, shown installed on anaircraft type spark plug,

FIG. 2 is an enlarged, fragmentary, vertical, sectional view of themoisture proof connector taken on the line 2-2 in FIG. 1, and

FIG. 3 is an enlarged, fragmentary, elevational view of the moistureproof connector with a portion thereof shown in cross section, and withthe spark plug proper shown in broken lines.

Referring to the drawing more particularly by reference numerals, 10indicates generally a moisture proof connector constructed in accordancewith the teachings of the present invention, shown in sealing engagementwith an aircraft type spark plug 12 of conventional design.

The plug 12 includes a cylindrical metal barrel 14 with an inner wall16, a chamfered upper end 18 and external threads 20 adjacent said upperend. Positioned within the barrel 14 is a tubular ceramic insulator 22which has an annular upper end 24 below the upper end 18 and which formsa well 26 within the interior of the spark plug. An electrical terminalor contact 28 is contained in the bottom of the well 26.

The moisture proof connector 10 includes an electrical cable 30 withseveral layers of insulation 32 thereon, the lower end of the cable(FIG. 2) having a bushing 34 swedged thereto, the lower end of thebushing being threaded to receive a nut 36 which has a coiled contactspring 38 mounted thereon, the contact spring being adapted to engagethe electrical terminal 28.

Positioned on the lower end of the insulated cable, 30, 32 is a tubulargrommet 40 of resilient, non-conductive material such as rubber andwhich includes a sleeve portion 42 having a bottom Wall with apassageway 43 which receives the bushing 34.

Intermediate the ends of the grommet 40 is an annular, externalprojection or collar 46 which provides an outer peripheral Wall surface48 of a diameter to fit within the plug barrel and engage the inner wallsurface 16 thereof, an upper shoulder 50, and a lower shoulder 52 whichhas a groove or kerf 54 adjacent the sleeve portion, the lower shoulderbeing adapted to engage the upper end of the tubular insulator 22.

- Vertically spaced internal annular flanges 44 and 45 are provided inthe interior of the sleeve portion 42 for sealing engagement with thesurface of the cable 30, 32, the flange 45 being in opposed relationshipwith the collar 46 for a purpose to appear.

Fitted on the grommet 40 above the projection or collar 46 is a rigidtubular metal ferrule 56, preferably made of brass, which includes alower end 58 in engagement with the upper shoulder 50 of the grommetprojection or collar. Intermediate the ends of the ferrule is an annularflange 60 which provides an upper shoulder 62 for supporting a freelyrotatable hold-down nut 64 which has inner threads 66 adapted to engagethe threads 20 on the plug barrel.

An annular groove 68 is provided in the body of the ferrule 56immediately beneath the flange 60, and positioned in said groove is anO-ring 70.

The upper end of the metal ferrule 56 is chamfered as at 72 to preventthe hold-down nut 64 from hanging up during the installation of theconnector, as will be discussed more fully hereinafter.

Positioned about the insulated cable 30, 32 and the upper end of thegrommet 40 is a wire-mesh, reinforced, insulated conduit 74 which hasthe lower end thereof fastened to the upper end of the metal ferrule 56.

The upper end of the electrical cable 30 and conduit 74 is ofconventional construction and does not form any part of the presentinvention.

In use, the end of the connector which contains the contact spring 38 isinserted into the barrel 14 of the spark plug as shown in FIG. 3, withthe outer peripheral wall surface 48 of the grommet collar 46 in asliding engagement with the inner wall 16 of the plug barrel.

The nut 64 is then moved downwardly or inwardly on the metal ferrule 56and sufficient pressure exerted by hand to cause the threads 66 of thenut 64 to engage the threads 20 of the plug barrel. The nut 64 is thenrotated by conventional means until the ferrule 56 and grommet 40 arefully seated within the plug barrel. As shown in FIG. 2, the axialdimensions of the connector 10 are such that when the O-ring 70 isseated on and in sealing engagement with the upper end 18 of the barrel14, the collar 46 is compressed between the lower end 58 of the ferruleand the upper end 24 of the insulator 22. The compression of the collar46 causes the lower shoulder 52 thereof to seat on the upper end 24 ofthe insulator 22 in sealing engagement, and, at the same time forces theinternal flange 45 into sealing engagement with the insulation 32 andthe outer peripheral wall surface 48 into sealing engagement wtih theinner wall surface 16 of the plug barrel 14. It should be noted that thegroove or kerf 54 in the lower shoulder 52 provides for additionallateral movement of the peripheral portion of the grommet collar 46 soas to increase the sealing engagement thereof, both with the upper end24 of the tubular insulator and with the inner wall surface of the plugbarrel 14.

Obviously, when the connector 10 is in sealing engagement with the plugbarrel as described hereinabove, the contact spring 38 is in engagementwith the terminal or contact 28 so as to provide an electricalconnection between the cable 30 and the terminal 28.

Thus, it is apparent that there has been provided a novel moisture proofconnector for spark plugs which fulfills all of the objects andadvantages sought therefor. The connector is relatively simple inconstruction and design and contains relatively few parts. Also, whenthe connector is fastened to a spark plug, the interior or well of theplug is sealed from the adjacent atmosphere by four different sealingsurfaces, thereby preventing the entrance of moisture and dirt into theplug well. In addition, the connector can be easily and quickly fastenedto an existing spark plug by even the most inexperienced personnelbecause it is merely necessary to insert the free end of the grommetinto the interior of the plug barrel, and thereafter engage and tightenthe hold-down nut.

It is to be understood that the foregoing description and theaccompanying drawing has been given only by way of illustration andexample, and that changes and alterations in the present disclosurewhich will be readily apparent to one skilled in the art, arecontemplated as within the scope of the present invention.

We claim:

1. A moisture proof connector for a spark plug which includes acylindrical barrel with an inner wall and an upper end, a tubularinsulator with an upper end positioned within the barrel, and a contactterminal within the insulator adjacent the lower end thereof,comprising:

an insulated electrical cable having contact means at one end thereoffor engagement with the contact terminal of the plug;

a tubular grommet of resilient material having one end thereof adaptedto fit within the tubular insulator of the plug, positioned on saidelectrical cable adjacent said one end thereof;

an external, annular collar on said grommet intermediate the endsthereof which provides an outer peripheral wall surface which fitswithin the barrel of the plug and which is adapted to engage the innerwall surface thereof, and

a lower shoulder adapted to seat upon the upper end of the tubularinsulator of the plug; and

means for selectively axially compressing said annular collar to forcethe lower shoulder thereof into sealing engagement with the upper end ofthe tubular insulator, and the outer peripheral wall surface thereofinto sealing engagement with the inner wall of the plug barrel.

2. A moisture proof connector for a spark plug which includes acylindrical barrel with an inner wall and an upper end, a tubularinsulator with an upper end positioned within the barrel, and a contactterminal within the insulator adjacent the lower end thereof,comprising:

an insulated electrical cable having contact means at one end thereoffor engagement with the contact terminal of the plug;

a tubular grommet of resilient material having one end therof adapted tofit within the tubular insulator of the plug, positioned on saidelectrical cable adjacent said one end thereof;

an external, annular collar on said grommet intermediate the endsthereof which provides an outer peripheral wall surface which fitswithin the barrel of the plug and which is adapted to engage the innerwall surface thereof, and

a lower shoulder adapted to seat upon the upper end of the tubularinsulator of the plug;

an internal, annular flange on said grommet in en gagement with theouter surface of said insulated electrical cable; and

means for selectively axially comprising said annular collar against theupper end of the tubular insulator, whereby to force the lower shoulderof the collar into sealing engagement with the upper end of the tubularinsulator, and the outer peripheral wall surface of the collar intosealing engagement with the inner wall surface of the plug barrel.

3. A moisture proof connector for a spark plug which includes acylindrical barrel with an inner wall and an upper end, a tubularinsulator with an upper end positioned within the barrel, and a contactterminal within the insulator adjacent the lower end thereof,comprising:

an insulated electrical cable having contact means at one end thereoffor engagement with the cont-act terminal of the plug;

a tubular grommet of resilient material having one end thereof adaptedto fit within the tubular insulator of the plug, positioned on saidelectrical cable adjacent said one end thereof;

an external, anular collar on said grommet intermediate the ends thereofwhich provides an outer peripheral wall surface which fits within thebarrel of the plug and which is adapted to engage the inner wall surfacethereof, and

a lower shoulder adapted to seat upon the upper end of the tubularinsulator of the plug;

at least two vertically spaced, internal, annular flanges on saidgrommet in engagement with the outer surface of said insulatedelectrical cable; and

means for selectively axially compressing said annular collar againstthe upper end of the tubular insulator, whereby to force the lowershoulder of the collar into sealing engagement with the upper end of thetubular insulator, and the outer peripheral wall surface of the collarinto sealing engagement with the inner wall surface of the plug barrel.

4. A moisture proof connector for a spark plug which includes acylindrical barrel with an inner wall and an upper end, a tubularinsulator with an upper end positioned within the barrel, and a contactterminal within the insulator adjacent the lower end thereof,comprising:

an insulated electrical cable having contact means at one end thereoffor engagement with the contact terminal of the plug;

a tubular grommet of resilient material having one end thereof adaptedto fit within the tubular insulator of the plug, positioned on saidelectrical cable adjacent said one end there-of;

an external, annular collar on said grommet intermediate the endsthereof which provides an outer peripheral wall surface which fitswithin the barrel of the plug and which is adapted to engage the innerwall surface thereof, and

a lower shoulder adapted to seat upon the upper end of the tubularinsulator of the plug;

an internal, annular flange on said grommet in engagement with the outersurface of said insulated electrical cable, said internal flange beingin opposed radial relationship with said external collar; and

means for selectively axially compressing said annular collar againstthe upper end of the tubular insulator, whereby to force the lowershoulder of the collar into sealing engagement with the upper end ofsaid insulator, the outer peripheral wall surface of the collor intosealing engagement with the inner wall surface of the plug barrel, andthe internal flange into sealing engagement with the outer surface ofthe insulated cable.

5. A moisture proof connector for a spark plug which includes acylindrical barrel with an inner wall and an upper end with externalthreads adjacent thereto, a tubular insulator with an upper endpositioned within the barrel, and a contact terminal within theinsulator adjacent the lower end thereof, comprising:

an insulated electrical cable having contact means at one end thereoffor engagement with the contact terminal of the plug;

a tubular grommet of resilient material having one end thereof adaptedto fit within the barrel of the plug, positioned on said electricalcable adjacent said one end thereof;

an external, annular collar on said grommet intermediate the endsthereof which provides an outer peripheral wall surface adapted toengage the inner wall surface of the plug barrel, and

a lower shoulder adapted to seat upon the upper end of the tubularinsulator of the plug;

a rigid tubular ferrule positioned on the tubular grommet above theannular projection thereof and adapted to fit within the plug barrel;and

means mounted on said ferrule for engagement with the threads of theplug barrel when said one end of the grommet is positioned within thebarrel, to compress the annular collar of the grommet to force the lowershoulder of said collar into sealing engagement with the upper end ofthe tubular insulator and the outer peripheral wall surface thereof intosealing engagement with the inner wall of the plug barrel.

6. A moisture proof connector for a spark plug which includes acylindrical barrel with an inner wall and an upper end, a tubularinsulator with an upper end positioned within the barrel, and a contactterminal within the insulator adjacent the lower end thereof,comprising:

an insulated electrical cable having contact means at one end thereoffor engagement with the contact terminal of the plug;

a tubular grommet of resilient material having one end thereof adaptedto fit within the tubular insulator of the plug, positioned on saidelectrical cable adjacent said one end thereof;

an external, annular collar on said grommet intermediate the endsthereof which provides an outer peripheral wall surface which fitswithin the barrel of the plug above the tubular insulator and which isadapted to engage the inner wall surface of said barrel, and

a lower shoulder adapted to seat upon the upper end of the tubularinsulator of the plug;

a tubular ferrule positioned on the grommet above one annular collar;

an O-ring mounted on the ferrule externally thereof and adapted toengage the upper end of the plug barrel when the lower shoulder of thecollar seats upon the upper end of the insulator; and

means for moving the ferrule axially and for compressing the collar ofthe grommet on the upper end of the tubular insulator to seat the O-ringon the upper end of the plug barrel, force the lower shoulder of theannular collar into sealing engagement with the upper end of the tubularinsulator, and expand the outer peripheral wall surface of the grommetcollar into sealing engagement with the inner wall of the plug barrel.

7. A moisture proof connector for a spark plug which includes acylindrical barrel with an inner wall and an upper end with externalthreads adjacent thereto, a tubular insulator with an upper endpositioned within the barrel, and a contact terminal within theinsulator adjacent the lower end thereof, comprising:

an insulated electrical cable having contact means at one end thereoffor engagement with the contact terminal of the plug; I a tubulargrommet of resilient material having one end thereof adapted to fitwithin the barrel of the plug, positioned on said electrical cableadjacent said one end thereof; an external, annular collar on saidgrommet intermediate the ends thereof which provides an outer peripheralwall surface adapted to engage the inner Wall surface of the spark plugbarrel, a lower shoulder adapted to seat upon the upper end of theinsulator of the plug, and an upper shoulder spaced axially of the lowershoulder; a rigid tubular ferrule positioned on the tubular grommetabove the annular collar thereof; an O-ring mounted on the ferruleexternally thereof for engagement with the upper end of the plug barrel;and fastening means mounted on the ferrule for adjustable holdingengagement with the threaded upper end of the plug barrel; the axial,dimensional relationship between grommet collar and the O-ring beingsuch that when the lower shoulder of said collar is in sealingengagement with the upper end of the tubular insulator, the O-ring isseated on the upper end of the plug barrel. 8. A moisture proofconnector for a spark plug which includes a cylindrical barrel with aninner wall and an upper end with external threads adjacent thereto, atubular insulator with an upper end positioned within the barrel, and acontact terminal within the insulator adjacent the lower end thereof,comprising:

an insulated electrical cable having contact means at one end thereoffor engagement with the contact terminal of the plug;

a tubular grommet of resilient material having one end thereof adaptedto fit within the barrel of the plug, positioned on said electricalcable adjacent said one end thereof;

an external, annular collar on said grommet intermediate the endsthereof which provides an outer peripheral wall surface which fitswithin the plug barrel and which is adapted to engage the inner surfacethereof, and a lower shoulder adapted to seat upon the upper end of theinsulator of the plug, and an upper shoulder spaced axially of the lowershoulder; a rigid, tubular ferrule with a lower end positioned on '7 thetubular grommet with said lower end in engagement with the uppershoulder of the collar;

an O-ring mounted on the ferrule externally thereof for engagement withthe upper end of the plug barrel; and

an internally threaded nut rotatably mounted on said ferrule and adaptedto enact with the threads on the plug barrel to axially move saidferrule toward the annular collar of the grommet, whereby when theO-ring is seated on the upper end of the plug barrel, the lower end ofthe ferrule compresses said annular projection against the tubularinsulator so as to seat the lower shoulder of the collar on the upperend of said insulator and cause the outer peripheral wall surface of thecollar to engage the inner surface of the barrel in sealing relationshiptherewith.

9. The combination of:

a spark plug which includes a cylindrical barrel with an inner wall andan upper end,

a tubular insulator with an upper end mounted within the barrel with theupper end of the insulator below the upper end of the barrel, and

a contact terminal within the insulator adjacent the lower end thereof;

an insulated electrical cable within the plug having contact means atone end thereof in engagement with the contact terminal of the plug;

a tubular grommet of resilient material mounted on said electrical cableand having one end thereof positioned within the tubular insulator ofthe plug;

an external, annular collar on said grommet above the upper end of thetubular insulator which provides a lower shoulder seated on the upperend of the insulator in sealing engagement therewith, and

an outer peripheral wall surface in sealing engagement with the innerwall surface of the barrel;

a rigid tubular ferrule with a lower end positioned on the grommet abovethe annular collar with the lower end thereof in compression engagementwith said collar;

an O-ring mounted on the ferrule externally thereof and in sealingengagement with the upper end of the plug barrel; and

means releasably maintaining said tubular ferrule in compressionengagement with the grommet collar.

10. The combination of:

a spark plug which includes a cylindrical barrel with an inner wall andan upper end,

a tubular insulator with an upper end mounted within the barrel with theupper end of the insulator below the upper end of the barrel, and

a contact terminal within the insulator adjacent the lower end thereof;

an insulated electrical cable within the plug having contact means atone end thereof in engagement with the contact terminal of the plug;

a tubular grommet of resilient material mounted on said electrical cableand having one end thereof positioned within the tubular insulator ofthe plug;

an external, annular collar on said grommet above the upper end of thetubular insulator which provides a lower shoulder seated on the upperend of the insulator in sealing engagement therewith, and

an outer peripheral wall surface in sealing engagement with the innerwall surface of the barrel;

an internal, annular flange on said grommet in sealing engagement withthe insulated electrical cable;

a rigid tubular ferrule with a lower end positioned on the grommet abovethe annular collar with the lower end thereof in compression engagementwith said collar;

an O-ring mounted on the ferrule externally thereof and in sealingengagement with the upper end of the plug barrel; and

means releasably maintaining said tubular ferrule in compressionengagement with the grommet collar.

References Cited UNITED STATES PATENTS 2,177,508 10/1939 Abbott 174-752,442,015 5/ 1948 Peters et al. 33984 2,442,858 6/1948 'Nims et a1.33994 2,651,298 9/1953 Brinson et a1. 313135 3,183,476 5/1965 Sacks etal 339 94 X MARVIN A. CHAMPION, Primary Examiner.

PATRICK A. CLIFFORD, Assistant Examiner.

1. A MOISTURE PROOF CONNECTOR FOR A SPARK PLUG WHICH INCLUDES ACYLINDRICAL BARREL WITH AN INNER WALL AND AN UPPER END, A TUBULARINSUATOR WITH AN UPPER END POSITIONED WITHIN THE BARREL, AND A CONTACTTERMINAL WITHIN THE INSULATOR ADJACENT THE LOWER END THEREOF,COMPRISING: AN INSULATED ELECTRICAL CABLE HAVING CONTACT MEANS AT ONEEND THEREOF FOR ENGAGEMENT WITH THE CONTACT TERMINAL OF THE PLUG; ATUBULAR GROMMET OF RESILIENT MATERIAL HAVING ONE END THEREOF ADAPTED TOFIT WITHIN THE TUBULAR INSULATOR OF THE PLUG, POSITIONED ON SAIDELECTRICAL CABLE ADJACENT SAID ONE END THEREOF; AN EXTERNAL, ANNULARCOLLAR ON SAID GROMMET INTERMEDIATE THE ENDS THEREOF WHICH PROVIDES ANOUTER PERIPHERAL WALL SURFACE WHICH FITS WITHIN THE BARREL OF THE PLUGAND WHICH IS ADAPTED TO ENGAGE THE INNER WALL SURFACE THEREOF, AND ALOWER SHOULDER ADAPTED TO SEAT UPON THE UPPER END OF THE TUBULARINSULATOR OF THE PLUG; AND